This invention relates to a method for hydrolyzing carbon oxysulfide, more particularly to a method whereby the hydrolysis is catalyzed by morpholines and piperazines.
Carbon oxysulfide or carbonyl sulfide (COS) is often present in minor amounts in petroleum refinery gases and it is found in larger amounts in coal gasification product streams. This toxic contaminant poses a special problem in sour gas purification processes since it is neither readily separated nor easily hydrolyzed by known gas treating solvents under ordinary conditions. It is an undesirable contaminant in a Claus plant feed stream, since it is not readily converted to sulfur, and it is necessary to remove it from fuel gases and the like for reasons of corrosion and air pollution. Carbon oxysulfide reacts irreversibly with ethanolamine but this is not usually a practical method for removing it from a gas stream because the solvent cannot be regenerated. The use of sulfolane, diisopropanolamine, methyldiethanolamine, and mixtures thereof are known to be useful to hydrolyze COS but the present invention gives a higher percent hydrolysis.
It is known from Belgium Pat. No. 750,177 that aqueous morpholine solution reacts with COS to form a precipitate which is recovered and subsequently treated to heat and pressure to recover morpholine. The present invention eliminates the need for the formation of a precipitate.
U.S. Pat. No. 4,100,256 describes a process for COS hydrolysis using an aqueous solution of piperazinone compounds however the present invention is more effective in that a higher degree of hydrolysis is obtained. For example, a 50% solution of morpholine gave 83% hydrolysis at 100.degree. C. and under the same conditions 1,4-dimethyl piperazinone gave 15% hydrolysis.